number of contestants in a challenge

[mammajamma]

I'm always befuddled by the high number of contestants set by a few challengers.
It's not that it makes your chance of winning more difficult but more so wondering if that many people will actually join in.
If the number is not attained, then I believe the challenge is tossed out.
Would you enter a challenge with 99 people? Or even 75?
I know that the challenger puts in a lot of time setting these games up as there is way more than one by an individual.
I don't enter these challenges so I don't see the final results.
Just curious to know if the majority of these get finalized.